The present invention relates to an optical transmission device and particularly to an optical transmission device suitable for interconnection in a portable electronic equipment that is small in size and elevation and that is indispensably adapted to surface mount.
Conventionally, optical transmission devices that use optical fiber cables as transmission media have a structure in which a fit position is determined and held by a plurality of outline surfaces of an optical plug. As examples of prior arts, optical transmission devices that are applied also to portable electronic equipment of consumer appliances will be described hereinbelow. In addition, reference will be made to a stacking-type electrical connector and an optical/electrical hybrid type plug connector.
Listed as a first prior art is an optical audio connector shown in FIGS. 6 through 8 (see JP H06-140106 A, for example). FIG. 6 shows a general view of an optical audio connector 100 and an optical plug 103, FIG. 7 shows a sectional view of the optical audio connector 100, and FIG. 8 shows a sectional view of the optical plug 103.
As shown in FIG. 7, a light emitting device 101 (or a light receiving device) is housed in a holder 104 in which a mechanism for holding the optical plug 103 fitted therein is provided. In the holder 104 is provided a hole 105 (shown in FIG. 6) for holding the optical plug 103 fit therein in a direction of an optical axis of the light emitting device 101. In this mechanism, the optical plug 103 is inserted into the hole 105 in the optical audio connector 100 in the direction of the optical axis of the light emitting device 101, so that the optical plug 103 is fitted and held in a specified position. On this occasion, protrusions 106 (shown in FIG. 8) provided on side surfaces of the optical plug 103 are guided into grooves 107 provided on inner side surfaces of the hole 105 (shown in FIG. 6) in the holder 104, so that positioning in a vertical direction and in a direction of the side surfaces is established. Besides, recesses 108 (shown in FIG. 8) provided in distal end part of the optical plug 103 are guided on and collide with protrusions 109 provided on a bottom surfaces in the hole 105 of the holder 104, so that positioning in a direction of depth thereof is established. Furthermore, protrusions 110 (shown in FIG. 8) provided on top and bottom surfaces of the optical plug 103 are fitted and held in pits 111 provided on top and bottom surfaces inside the hole 105 of the holder 104. In order to fit and hold the optical plug 103 in the holder 104, therefore, the holder 104 has to be provided so as to cover the top and bottom surfaces and both the side surfaces of the optical plug 103.
Listed as a second prior art is an optical connector for portable audio equipment shown in FIGS. 9 and 10 (see JP H06-140106 A, for example). FIG. 9 shows a sectional view of the optical connector 200 for portable audio equipment and FIG. 10 shows an external view of an optical plug.
As shown in FIG. 9, a light emitting device 201 (or a light receiving device) is housed in a holder 204 in which a mechanism for holding the optical plug 203 fitted therein is provided. In the holder 204 is provided a hole 205 for holding the optical plug 203 fitted therein in a direction of an optical axis. In this mechanism, the optical plug 203 is inserted into the hole 205 in the direction of the optical axis of the light emitting device 201, so that the optical plug 203 is fitted and held in a specified position. On this occasion, tapered part 206 provided at distal end of the optical plug 203 is guided into cone-like guide part 207 provided in the holder 204, so that positioning in a direction perpendicular to the optical axis is established. In addition, a step 208 provided at root of the optical plug 203 collides with a wall 209 of the holder 204 in which the hole 205 is provided, so that positioning in the direction of the optical axis is established. Furthermore, constricted part 210 of the optical plug 203 is pressed and held by metal pieces 211 that have spring ability and that are provided in the hole 205 of the holder 204. In order to fit and hold the optical plug 203 in the holder 204, therefore, the holder 204 has to be provided so as to cover the tapered distal end part 206 of the optical plug 203 and a whole volume of the plug 203.
Listed as a third prior art is a stacking-type electrical connector shown in FIGS. 11A and 11B (see JP H07-16381 U, for example).
In the stacking-type electrical connector, as shown in FIG. 11A, paired contacts are rubbed by fitting against each other so as to acquire electrical contact. Contacts 301 on one side of the paired contacts are each bifurcated into plate-like distal end parts having elasticity in a direction of thickness thereof, and contacts 302 on the other side are shaped so as to fit in inside of the bifurcated parts.
A branch 344 in the bifurcated part of the contact 301 on one side has electrical contact part 345 on inside of the bifurcated part and is thereby brought into electrical contact with the contact 302 on the other side. Between the other branch 346 in the bifurcated part of the contact 301 and the contact 302 on the other side is provided a lock mechanism composed of a combination of a protrusion 303 and a recess 304 into which the protrusion 303 is to fall.
In the stacking-type electrical connector, as shown in FIG. 11B, the protrusion 303 can be prevented from easily slipping out of the recess 304, by a structure in which the bifurcated contact 301 on one side elastically pinches the contact 302 on the other side and in which the protrusion 303 falls into the recess 304.
Listed as a fourth prior art is an optical/electrical hybrid type plug connector shown in FIGS. 12 and 13 (see LP 2002-182070 A, for example).
As shown in FIG. 12, a connector 510 has a receptacle 505 into which two plugs 500 can be connected. As shown in FIG. 13, the plug 500 is composed of a fiber support device 502 for supporting an optical fiber extending through a front opening of an insulator housing 501, a cantilever latch 503 provided on upper part of the insulator housing 501, and metal blades 504 provided on bottom surface side of the insulator housing 501.
The cantilever latch 503 is a mechanism that lockably meshes with the receptacle 505 to be connected thereto. The optical/electrical hybrid type plug connector is suitable for high-density panel mounting because the cantilever latch 503 is placed on top of the insulator housing 501 and because electrical connection device 504 is placed on the bottom surface side of the insulator housing 501. Such a structure prevents interference of the latching structure with left and right sides of the plug connector. In fact, this jack structure has receptacles that are spaced (arranged) at small interval and that can be used for high-density application, because only minimum spaces are required between side surfaces thereof.
In the receptacle 505 are provided a hole 506 for holding the fiber support device 502 provided in the plug, terminals 507 to which the metal blades 504 are to be electrically connected, and lock holes 508 for holding the cantilever latch 503 fitted therein.
The fit of the plug connector is achieved by movement of the fiber in the axial direction. The plug connector is designed so that the fiber support device 502 enters the receptacle 505 before electrical plug components (504, 507) are engaged, and thus an LC type optical plug that does not have the metal blades 504 can also be fitted in and held by the receptacle.
As described above, the first and second prior arts require the holder that is configured so as to cover an outside shape of the optical plug. Such a configuration is a great restriction on size reduction and requires the optical plug to be inevitably moved in the direction of the optical axis of the optical fiber when the optical plug is inserted into or extracted from the holder. Thus an area larger than the optical plug in length is required on a printed board in order that the optical plug is inserted into or extracted from the holder, and any components cannot be placed at all in the area. Therefore, the optical transmission devices of the first and second prior arts are not suitable for portable electronic equipment, which has been being decreased in size and thickness.
In the third prior art, electrical connection and fitting can be achieved by a small and thin configuration, whereas the prior art provides a mechanism only for implementing electrical contacts and does not provide a mechanism for precisely positioning the plug connector necessary for optical connection, a mechanism for holding the plug connector with a fit, and the like.
The fourth prior art provides the optical/electrical hybrid plug connector, which has a structure having the metal blades for electrical contacts provided in a part of the optical plug, and the plug is inserted in the direction of the optical axis of the optical fiber as in the first and second prior arts. Therefore, the fourth prior art is not suitable for portable electronic equipment, which has been being decreased in size and thickness.